Now that we have covered some common pain points that affect XenApp customers, let’s discuss how server virtualization can address each of these points. In general, there are three main benefits that server virtualization can deliver to the XenApp environment.First, server virtualization can provide significant cost-savings through server consolidation. Underutilized XenApp servers and application silos can be consolidated, thus maximizing the return on investment for existing IT resources, minimizing the server footprint in the datacenter, and increasing server utilization. Additionally, the levels of isolation and scalability offered by 64-bit platforms allow multiple 32-bit workloads to be consolidated on higher-capacity, more cost-effective 64-bit servers.Server virtualization introduces a new, simplified management paradigm for XenApp environments. For example, you can now manage and provision XenApp servers across both physical and virtual server infrastructures, increasing flexibility in testing, development, production, and disaster recovery environments. You can dynamically provision new XenApp servers as business needs dictate, such as the month-, quarter-, or year-end, when traffic to line-of-business applications tend to be the highest. Moreover, since a single XenApp server image can be used to bootstrap both physical and virtual servers, it has become far easier to move XenApp servers farms between a physical infrastructure (such as a primary datacenter deployment) and a virtual infrastructure (such as a disaster recovery site).Finally, server virtualization can enhance the availability of XenApp applications. For example, XenServer effectively decouples application uptime from potential issues with the underlying hardware. Furthermore, capabilities like rapid server provisioning can simplify disaster recovery strategies, which are critically important in the event of a total datacenter failure.
XenServer can help address some of the scaling challenges with XenApp. Today, processor technology has progressed to the point where unvirtualized, physical 32-bit XenApp servers end up with unused processor capacity. Typical XenApp server hardware features dual socket, quad-core processors. Yet 32-bit Windows can natively address only 4 GB of RAM, so you tend to end up with servers that aren’t using this processor capacity very effectively. The graph here illustrates this, in that with memory fully utilized, there is as much as 80% processor availability. This is capacity that XenServer can help you make use of.
As a result, we see that XenServer is able to support 41% more users per host than VMware and delivered excellent performance at high user counts.Interestingly, we’ve heard anecdotally from partners and customers on even more impressive results—up to 2x more users for XenApp with XenServer compared to VMware.
We often get asked how we’re able to get such great performance.It really comes down to three things.Hardware Virtualization Assist The efficiency of the Xenhypervisor, which we see across the board for all workloads both Linux and Windows-basedOne-click shadow memory multiplier optimizer, specifially the shadow memory multipler
Finally, we have made it really simple to implement the optimizations. No complex tweaking is required. When you have a VM running XenAp, you go to the optimization tab and just select “optimize for XenApp.” Now, underneath this setting is a lot of Citrix R&D investment. We understand the XenApp workload better than anyone, and we’ve put the XS and XA engineering teams together to derive this simple solution. Essentially, what this setting allows XenServero be much more efficient in the management of memory, preventing the "thrashing" that occurs as XenApp processes create and destroy shadow pagetables. XenApp is a unique in how often these page tables are created an destroyed, so we’ve derived this optimization to accommodate the workload more effectively.More information is available here: http://community.citrix.com/blogs/citrite/anilma/2008/08/04/Shedding+some+light+on+XenApp+on+XenServer+performance+tuning
The performance testing toolkit, available from the XenServer SDK site, actually contains everything you’d need to re-create the tolly study in house – including the EdgeSight for Load Testing script and some sample results to analyze.
Market reaction has been amazing and we already see people taking a look at XenServer who wouldn’t have before.